In the inflammatory reactions, it is generally understood that when a microorganism invades a tissue or when the tissue is injured, leukocytes play an important role for the exclusion of the microorganism or for the repair of the injured tissue. It is also widely understood that in such cases, leukocytes usually circulating in the blood must pass through the vascular wall and be newly supplied to the injured tissue. It has been elucidated that the infiltration of the leukocytes from the blood vessel into the tissue is carried out by integrin molecules which are a group of heterodimeric proteins expressing on the leukocytes. The integrin molecules are classified into at least 8 subfamilies (β1 through β8 subfamilies) depending on the β chains thereof. Known typical subfamilies are β1 and β3 subfamilies involved in the adhesion of cell ingredients to the extracellular matrix such as collagen and fibronectin; β2 subfamily involved in cell-to-cell adhesion in the immune system; and β7 subfamily which mainly participates in the infiltration of leukocytes into mucosal tissues (Nonpatent Literature 1). As for the above-described α4 integrins, two kinds of molecules thereof are known. They are VLA-4 (very late antigen-4) molecule belonging to the β1 subfamily and comprising α4β1 chain and LPAM-1 (lymphocyte Peyer's patch HEV adhesion molecule-1) molecule belonging to the β7 subfamily and comprising α4β7 chain. Usually most of leukocytes circulating in the blood have only a low adhesion affinity for the vascular-endothelium cells and they cannot move out of the blood vessel. However, lymphocytes mainly comprising T cells and B cells are capable of moving out of the blood vessel by a so-called lymphocyte homing phenomenon wherein they move from the blood into the lymphoid tissue through the blood vessel wall and then they return into the blood through the lymphatic vessel under the physiological conditions. It is known that LPAM-1 molecules participate in the lymphocyte homing into the lymphoid tissue of an intestinal tract such as Peyer's patch (Nonpatent Literature 2). On the other hand, when an inflammation occurs, the vascular-endothelium cells are activated by cytokine and chemokine released from the inflamed tissue, the expression of a group of cell surface antigens (adhesion molecules) participating in the adhesion of leukocytes to the vascular-endothelium cells is caused, and a lot of leukocytes infiltrate out of the blood vessel toward the inflamed tissue through the adhesion molecules.
As the cell surface antigens on the vascular-endothelium cells participating in the adhesion of the leukocytes, there have been known E-selectin (adhesion molecule mainly participating in the adhesion of neutrophils), ICAM-1 and VCAM-1 mainly participating in the adhesion of lymphocytes, and MAdCAM-1 mainly participating in the adhesion of lymphocytes in the lymphoid tissue of an intestinal tract such as Peyer's patch (Nonpatent Literature 1). It was reported that in those adhesion molecules, VCAM-1 acts as a ligand of both VLA-4 and LPAM-1 and that MAdCAM-1 acts as the ligand of LPAM-1. As a ligand of both VLA-4 and LPAM-1, fibronectin which is a kind of extracellular matrix is also known (Nonpatent Literature 1). The β1 integrin subfamily to which VLA-4 belongs comprises at least 6 integrins (VLA-1 to VLA-6) using extracellular matrixes such as fibronectin, collagen and laminin as the ligands. Many of integrins using extracellular matrixes as the ligands, such as VLA-5, β3 subfamily and β5 subfamily, recognize arginine—glycine—aspartic acid (RGD) sequence in fibronectin, vitronectin, tenascin and osteopontin. On the other hand, in the interaction of VLA-4 and fibronectin, the RGD sequence does not participate but a CS-1 peptide segment comprising leucine—aspartic acid—valine (LDV) as the core sequence participates (Nonpatent Literature 3). Clements et al. found a sequence similar to LDV in amino acid sequences of VCAM-1 and MAdCAM-1. It has been elucidated that a variant obtained by partially modifying the CS-1-like sequence of VCAM-1 and MAdCAM-1 molecules cannot interact to VLA-4 or LPAM-1 (Nonpatent Literatures 4 to 7). Thus, it was found that the CS-1-like sequence is important for the interaction of VLA-4/LPAM-1 and VCAM-1/MAdCAM-1.
It was also reported that the cyclic peptide having the CS-1-like structure is antagonistic both to the interaction of VLA-4 or LPAM-1 with VCAM-1, MAdCAM-1 or CS-1 peptide (Nonpatent Literature 8). The above-described facts indicate that all the interactions of α4 integrin and VCAM-1, MAdCAM-1 or fibronectin can be blocked by using a suitable α4 integrin antagonist (the term “α4 integrin antagonist” in the specification indicates a substance antagonistic to a 4β1 and/or α4β7 integrin).
It is also known that the expression of VCAM-1 in vascular-endothelium cells is caused by inflammatory factors such as LPS, TNF-α or IL-1 and that when the inflammation occurs, the infiltration of the leukocytes from the blood vessel into the tissue is carried out by the VLA-4/VCAM-1 adhesion mechanism (Nonpatent Literatures 9 to 11). Because VLA-4 is expressed on the surfaces of activated lymphocytes, monocytes, eosinophils, mast cells and neutrophils, the adhesion mechanism of VLA-4/VCAM-1 plays an important role for the infiltration of those cells into the inflamed tissue. It was reported that VLA-4 is expressed on various sarcoma cells such as melanoma cells, and it was also elucidated that the adhesion mechanism of VLA-4/VCAM-1 participates in the metastasis of these tumors. By investigating the expression of VCAM-1 in various pathological tissues, it was made apparent that the adhesion mechanism of this VLA-4/VCAM-1 participates in various pathological stages. Namely, it was reported that in addition to the activated vascular-endothelium cells, the expression of VCAM-1 is increased in the inflamed tissues in the patients with autoimmune diseases such as rheumatoid synovial membrane (Nonpatent Literatures 12 and 13), lungs and respiratory tract epithelium in asthma (Nonpatent Literature 14) and allergic diseases (Nonpatent Literature 15), systemic lupus erythematosus (Nonpatent Literature 16), Sjögren's syndrome (Nonpatent Literature 17), multiple sclerosis (Nonpatent Literature 18) and psoriasis (Nonpatent Literature 19); atherosclerotic plagues (Nonpatent Literature 20), intestinal tissues of the patients with inflammatory bowel diseases such as Crohn's disease and ulcerative colitis (Nonpatent Literatures 21 and 22), inflamed tissue of Langerhans islet of patients with diabetes (Nonpatent Literature 23) and implants during the rejection of transplantation of heart or kidney (Nonpatent Literatures 24 and 25). The adhesion mechanism of VLA-4/VCAM-1 participates in these various diseases.
There are many reports showing that in vivo administration of VLA-4 or VCAM-1 antibody was effective in improving the diseases of animal models with those inflammatory diseases. Concretely, Yednock et al. and Baron et al. reported that the in vivo administration of an antibody against a 4 integrins was effective in controlling the incidence rate or in controlling encephalomyelitis in the experimental autoimmune encephalomyelitis models, i.e. multiple sclerosis models (Nonpatent Literatures 26 and 27). Zeidler et al. reported that in vivo administration of an antibody against α 4-integrin was effective in controlling the incidence rate of mouse collagen arthritis (rheumatoid models) (Nonpatent Literature 28). The therapeutic effect of an antibody against α4-integrin in asthma models was reported by Abraham et al. and Sagara et al. (Nonpatent Literatures 29 and 30). The effect of an antibody against α4-integrin in inflammatory bowel disease models was reported by Podolsky et al. (Nonpatent Literature 31). The effect of an antibody against α4-integrin and that against VCAM antibody in insulin-dependent diabetes models were reported by Baron et al. (Nonpatent Literature 32). It was made apparent with baboon models that the restenosis of a blood vessel after an angioplasty carried out because of arteriosclerosis can be inhibited by the administration of α4 integrin antibody (Nonpatent Literature 33). It was also reported that α4 integrin or VCAM antibody is effective in inhibiting the rejection of an implant or inhibiting metastasis of a cancer (Nonpatent Literatures 34 and 35). The therapeutic effect of an antibody against VCAM-1 in inflammatory bowel disease models was reported by Sans et al. (Nonpatent Literature 44).
As described above, unlike VCAM-1, MAdCAM-1 which is a ligand of LPAM-1 is constitutively expressed on high endothelial venules (HEV) in the intestinal mucosa, mesenteric lymphatic nodes, Peyer's patch and spleen and it participates in the homing of mucosal lymphocytes. It is also known that LPAM-1/MAdCAM-1 adhesion mechanism not only has physiological roles in the homing of the lymphocytes but also participates in some pathological processes. Briskin et al reported an increase in the expression of MAdCAM-1 in inflamed regions in intestinal tracts of patients with inflammatory bowel diseases such as Crohn's disease and ulcerative colitis (Nonpatent Literature 36). Hanninen et al. reported that induction of the expression is observed in an inflamed tissue of Langerhans islet of NOD mouse which is a model of an insulin-dependent diabetes (Nonpatent Literature 37). The fact that LPAM-1/MAdCAM-1 adhesion mechanism participates in the progress of diseases is apparent from the fact that conditions of mouse models with inflammatory bowel disease (Nonpatent Literature 38) and the above-described NOD mouse models are improved by the in vivo administration of antibody to MAdCAM or antibody to β7 integrin (Nonpatent Literatures 39 and 40).
The above-described facts indicate the possibility in that employing the blocking of VLA-4/VCAM-1, LPAM-1/VCAM-1 or LPAM-1/MAdCAM-1 adhesion mechanism by a suitable antagonist is effective in treating the chronic inflammatory diseases described above. Regarding the therapeutic effects of the suitable antagonist(s), they can be ensured by the animal models described in the above literatures or the other literatures such as Nonpatent Literature 45 and 46. The use of the antibody against VLA-4 as the VLA-4 antagonist is described in Patent Literatures 1 to 4. Peptide compounds as VLA-4 antagonists are described in Patent Literatures 5 to 8. Amino acid derivatives usable as VLA-4 antagonists are described in Patent Literatures 9 to 13. The low-molecular α4 integrin inhibitor which can be orally administered is described in Patent Literatures 14 and 15.
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